Immune system can use melanoma's own proteins to kill off cancer cells, TAU researchers find. Though a small group of proteins, the family called Ras controls a large number of cellular functions, including cell growth, differentiation, and survival. And because the protein has a hand in cellular division, mutated Ras, which can be detected in one-third of all tumors, contributes to many human cancers by allowing for the rapid growth of diseased cells.